This invention relates generally to apparatus for controlling electrical power consumption of voltage regulatable loads such as lighting loads in office buildings, industrial plants, schools and other like buildings. More particularly, the invention relates to voltage control apparatus for three phase power sources whereby power consumption can be regulated.
Energy conservation is a major concern today. One effective method of conserving energy is through regulation of power consumption whereby unnecessary power usage is eliminated. Prior art devices for regulating lighting loads, for example, are known which include transformers connected in either a bucking or boosting circuit configuration. Such transformers normally form a static condition without any dynamic control. The absence of dynamic control either makes is impossible to trigger fluorescent lamps or alternatively prevents normal operation of fluorescent lamps when the voltage level drops too low or rises too high. For these reasons, such transformers generally have not been employed to control fluorescent lamp circuits.
Prior art transformer devices which have controls such as variacs generally have not had adequate sensing circuits to provide for the desired control of power consumption and lighting loads.
Regulators for lighting loads have also employed solid state elements. Such solid state elements are generally phase controlled devices which have a number of undesirable characteristics. For example, they tend to cause a significant amount of radio frequency interference (RFI). Further, they are not generally useable with fluroescent lights without some special provision in the fluorescent ballasts and auxiliary controls. Additionally, there is generally no protection against voltage surges in the triac, the diac, or other solid state developments. This absence of protection frequently causes the solid state control element to be damaged upon the occurence of a burnout of the lamp.
Disclosed in co-pending application Ser. No. 839,748, filed Oct. 5, 1977 (filed by the present applicant) is a single phase power control unit which is particularly useful for lighting loads such as incandescent lamps and fluorescent lamps. The power control unit is located between the power source and the load, typically between the circuit breaker and the lamps in a single circuit. The power control unit functions to reduce the voltage delivered to the load and thereby reduce the power consumed by the load. Reductions in power up to 10% or more are possible without any significant loss in lighting usefulness. Savings up to 40% or more are possible when significant reductions in lighting output are acceptable. The unit includes means for controlling operations as a function of voltage levels, delay times, clock times, and external conditions. The unit can automatically reduce the output voltage level with means for directly applying the input voltage level if the output voltage level drops below a predetermined threshold. Additionally, the unit includes delay means for timing periods when the output voltage to the load is either maintained at a reduced level or maintained at a non-reduced level. For example, the output is maintained at reduced level for a majority of time except that periodically, the output voltage is returned to a high level for short periods of time. Each time the output is returned to a high level, any fluorescent load on the line can be switched on.